Leucism is a term for reduced pigmentation in animals. This condition is distinguished from albinism in that it is caused by a reduction in all types of skin pigments, not just the pigment, melanin. Albinism results in the reduction of melanin pigment production only. Leucistic animals are a phenotype resulting from defets in pigment cell differentiation and/or, migration from neural crest cells (the precursors of melanin-producing cells) to skin, hair or feathers during development.
Leucistic hummingbirds are rare but are seen more often than true albino hummingbirds. Like normal hummingbirds they have black eyes, feet, and bill but their feathers may be pure white, buffy, tan, or gray instead of green or some other "normal" color.
This gallery presents a leucistic Ruby-throated Hummingbird (Archilochus colubris). According to Fred Bassett, a Hummingbird specialist in Montgomery, AL, this is an immature bird, most probably a female. A normal Ruby-throated Hummingbird is included at the end of the gallery for comparison.
I acknowledge the assistance of Roger Johnson, who called this hummingbird to my attention and gave me the opportunity to obtain these images. Thank you Roger.
For photos of another leucistic immature female Ruby-throated Hummingbird which was banded, go to http://www.hummingbirds.net/whitworth.html Courtesy of Hummingbirds.net, Lanny Chambers and Dave Whitworth, the photographer.